A bunghole is a hole bored the head-end or in a side stave of a liquid-tight wooden barrel. The hole is capped with a large cork-like object called a bung. Bungholes were first used on wooden barrels, and were typically bored by the purchaser of the barrel using a brace and bit. Bungholes can be bored in either head (end) of a barrel or in one of the staves (side). With the bung removed, a tapered faucet can be attached to aid with dispensing. When barrels full of a commodity such as wine, beer or spirits were shipped, the recipient would often bore new bungholes of the most suitable size and placement rather than remove the existing bung. Wooden barrels manufactured by specialty firms today usually are bored by the maker with suitable bungholes, since the users who purchase them for the making of beer, wine, and fermented foods often do not have a suitable brace and bit. Indeed, pre-drilled barrel bung holes are now the industry standard.
Wine and spirits barrel bungs are traditionally made of cork, wood or a slightly resilient plastic, and are monolithic in nature and configuration. A bung is truncated cylindrical or conical closure to seal a container, such as a bottle, tube or barrel. Unlike a lid which encloses a container from the outside without displacing any inner volume, a bung is partially inserted into the container from the exterior to act as a seal. A rubber stopper is sometimes called a rubber bung, and a cork stopper is called a cork. Stoppers used for wine bottles are typically referred to as “corks”, even though made from another material, typically a specialty plastic that has the correct modulus of elasticity to permit the high degree of compression to fit into the neck of the bottle and thereafter expand to make a tight seal.
When the hole to be sealed is large, as in the case of a barrel, the stopper is called a bung. When small, such as the stopper of a wine bottle they are called plugs, stoppers or corks. Other bungs, particularly those used in chemical barrels, may be made of metal and are screwed into place via threading, or may be made of hardened rubber. Other types of all-plastic plugs are commonly used to prevent the air from leaking out the filler tube of an inflated air-bed. This type of stopper is commonly made in two parts; the plastic outer screw-on cap and the inner rubber plug or stopper used to seal the tubing.
Glass stoppers are used in chemistry applications and in some decanters of wine or spirits. Typically the sides of the stopper and the inner matching bore of the chemical flask or decanter are ground with mating tapers to provide an air and fluid tight seal.
However, wine and spirit barrel bungs are commodity items, usually not made with any precision, and may ordinarily be seated with wood or leather mallets. They often crack upon use and are considered a disposable item. In the case of elastomeric bungs, they may include an exterior flange to prevent them from being pushed inside the barrel as they deform too easily, and care must be taken in setting them properly in the bunghole, seated deeply enough that they make a good seal, but not so deep that they cannot be removed. This is particularly problematic in the case of wine and spirits aging, where the bung must seal tightly, but also protrude enough to provide a hand-grippable projecting portion.
Accordingly, there is a need in the art for a bung that is universal in size, provides a tight edge seal when seated in a bunghole of both new and older, used barrels, is easily graspable by hand, and is resistant to being over-seated and lost inside the barrel.